Built-in test for high-speed electrical networks

Abstract

An apparatus for providing auxiliary signals on a high speed electrical signal network is provided such that the auxiliary signals may be used for independent monitoring or communication of monitored information without affecting data or bit error rates for the primary high speed data signals. The auxiliary signals may be used as part of a built-in testing of a network, including electrical time-domain reflectometry measurements to determine fault locations in a network.

1. An apparatus for performing electrical time-domain reflectometry on an electrical network having a transmission line, the apparatus comprising:
 an output stage comprising an electrical signal source adapted to provide a high-speed data signal extending over a high frequency range and having a first maximum peak-to-peak value, the signal source adapted to provide an auxiliary data signal extending over a low frequency range below the high frequency range and having a second maximum peak-to-peak value smaller than the first maximum peak-to-peak value, wherein the second maximum peak-to-peak value is at least two orders of magnitude smaller than the first maximum peak-to-peak value; 
 a controller coupled to the electrical signal source for controlling the electrical signal source to produce the high-speed data signal and for modulating the high-speed data signal with the auxiliary data signal; and 
 a testing stage for sending a pulse on the transmission line, the testing stage comprising a receiver coupled to receive a reflected portion of the pulse, the receiver comprising, a sample-and-hold device adapted to store the reflected portion, and the testing stage further comprising a variable delay device coupled to the sample-and-hold device for controlling a timing interval of the storage; 
 wherein the controller is further coupled to the receiver and configured to measure a timing of the received reflected portion of the pulse to determine where in the electrical network a fault is occurring. 
 
     
     
       2. The apparatus of  claim 1 , wherein the high frequency range of the high-speed data signal extends from a frequency of at least 10 MHz or higher, and wherein the low frequency range of the auxiliary signal is at least 1 kHz or below. 
     
     
       3. The apparatus of  claim 1 , wherein the high frequency range of the high-speed data signal has a low cut-off frequency, and wherein the low frequency range of the auxiliary data signal has a high cut-off frequency that is at least two orders of magnitude lower than the low cut-off frequency. 
     
     
       4. The apparatus of  claim 1 , wherein the testing stage comprises a variable delay circuit and a signal source coupled to the variable delay circuit for producing the pulse. 
     
     
       5. The apparatus of  claim 4 , wherein the signal source of the testing stage is different than the signal source of the output stage. 
     
     
       6. The apparatus of  claim 1 , wherein the controller is configured to produce auxiliary data in response to the measuring of the timing of the received reflected portion of the pulse. 
     
     
       7. The apparatus of  claim 1 , wherein the pulse comprises a narrow pulse of approximately 1 nanosecond. 
     
     
       8. The apparatus of  claim 1 , wherein the testing stage is for sending spaced-apart pulses on the transmission line, the spaced-apart pulses are spaced-apart by a repetition rate approximating a round-trip time between known network devices, the receiver is coupled to receive the reflected portion of the spaced-part pulses, and the controller is configured to measure the timing of the received reflected portion of the spaced-apart pulses, including at least one of measuring a pulse width of the spaced-apart pulses, measuring the repetition rate of the spaced-apart pulses, or measuring a time between the sending of the spaced-apart pulses and the receipt of the received reflected portion of the spaced-apart pulses in order to determine a location of where in the electrical network the fault is occurring. 
     
     
       9. The apparatus of  claim 8 , wherein the controller is further configured to determine a source of the received reflected portion of the spaced-apart pulses in order to determine a cause of the fault. 
     
     
       10. A method of performing electrical time-domain reflectometry on an electrical network having a transmission line, the method comprising:
 providing a high-speed data signal, using an electrical signal source, wherein the high-speed data signal extends over a high frequency range and has a first maximum peak-to-peak value; 
 providing an auxiliary data signal, using the electrical signal source, wherein the auxiliary data signal extends over a low frequency range below the high frequency range and has a second maximum peak-to-peak value smaller than the first maximum peak-to-peak value, the second maximum peak-to-peak value being at least two orders of magnitude smaller than the first maximum peak-to-peak value; 
 controlling the electrical signal source to modulate the high-speed data signal with the auxiliary data signal; 
 sending a pulse on the transmission line; 
 receiving a reflected portion of the pulse; and 
 determining where in the electrical network a fault is occurring by measuring a timing of the received reflected portion of the pulse. 
 
     
     
       11. The method of  claim 10  wherein the controlling is done using a controller coupled to the electrical signal source. 
     
     
       12. The method of  claim 11  wherein the controller produces the high-speed data signal. 
     
     
       13. The method of  claim 11  wherein the controller modulates the high-speed data signal. 
     
     
       14. The method of  claim 10  wherein the sending is done using a testing stage. 
     
     
       15. The method of  claim 10  wherein the receiving is done using a receiver. 
     
     
       16. The method of  claim 15  wherein the receiver is coupled to a testing stage which does the sending of the pulse on the transmission line. 
     
     
       17. The method of  claim 10  further comprising storing the reflected portion of the pulse. 
     
     
       18. The method of  claim 17  wherein a receiver stores the reflected portion of the pulse using a sample-and-hold device. 
     
     
       19. The method of  claim 17  further comprising controlling a timing interval of the storage. 
     
     
       20. The method of  claim 19  wherein a receiver controls the timing interval of the storage using a variable delay device. 
     
     
       21. The method of  claim 10  wherein the high frequency range of the high-speed data signal extends from a frequency of at least 10 MHz or higher, and wherein the low frequency range of the auxiliary signal is at least 1 kHz or below. 
     
     
       22. The method of  claim 10  wherein the high frequency range of the high-speed data signal has a low cut-off frequency, and wherein the low frequency range of the auxiliary data signal has a high cut-off frequency that is at least two orders of magnitude lower than the low cut-off frequency. 
     
     
       23. The method of  claim 10  further comprising producing the pulse using a variable delay circuit and another signal source coupled to the variable delay circuit. 
     
     
       24. The method of  claim 23  wherein the another signal source is different than the electrical signal source. 
     
     
       25. The method of  claim 10  further comprising producing auxiliary data in response to the measuring the timing of the received reflected portion of the pulse. 
     
     
       26. The method of  claim 25  wherein a controller coupled to a receiver measures the timing of the received reflected portion of the pulse, and produces the auxiliary data in response to the measuring of the timing of the received reflected portion of the pulse. 
     
     
       27. The method of  claim 10  wherein the pulse comprises a narrow pulse of approximately 1 nanosecond. 
     
     
       28. The method of  claim 10  wherein the sending the pulse on the transmission line comprises sending spaced-apart pulses on the transmission line which are spaced-apart by a repetition rate approximating a round-trip time between known network devices, the receiving the reflected portion of the pulse comprises receiving the reflection portion of the spaced-apart pulses, the determining where in the electrical network the fault is occurring by measuring the timing of the received reflected portion of the pulse comprises at least one of measuring a pulse width of the spaced-apart pulses, measuring the repetition rate of the spaced-apart pulses, or measuring a time between the sending of the spaced-apart pulses and the receipt of the received reflected portion of the spaced-apart pulses in order to determine a location of where in the electrical network the fault is occurring. 
     
     
       29. The method of  claim 28  wherein the determining where in the electrical network the fault is occurring by measuring the timing of the received reflected portion of the pulse further comprises determining a source of the received reflected portion of the spaced-apart pulses in order to determine a cause of the fault.